Local shop, JPM Supply (google it) has 240-43 toroids for $8.50 each. Orders arrive in my mailbox in a day or two.
73 Mark K5MGJ > On Mar 27, 2020, at 5:12 PM, Rick Hiller via BVARC <[email protected]> wrote: > > > Tell you what I would do, Marty......Get you some T-200-43 torroids and wind > your coax thru these a few times at about 35 feet below the feed point. Then > I would also do the same, or make a 10" dia coil of 8 or so turns of coax on > a form right where the coax enters into the shack. Further details on this > have a read of Jim Browns article -- ' > http://www.w4ava.org/articles/k9yc-rfi.pdf > > This antenna will certainly generate common mode currents on the feed line. > And whether they use that to accentuate the performance or not, these > currents will cause you problems in the shack. > > Certainly try to get the antenna up to 35 feet or so. By doing so also gets > you above the buildings and noise, etc. And most important, it will see the > horizon in a single story house neighborhood. I had a 40 meter ground plane > vertical up at about 40 feet years back and it worked gangbusters. > > There is alot of information on the web about this antenna..... or really > about the Comet, Diamond or Eagle versions of this design. MFJ licenses the > design and manufacturing from Comet. Google "N6PET Comet Antenna CHA-250". > He describes what is inside the matching xfmr and his take on performance. > Even Monitoring Times got into the picture with a comparison review with the > GAP Titan. Gooogle that too. > > On the higher bands it might do OK, especially if you get it higher in the > air. But not on the lower bands 40 and below.... just because it is quite a > compromise -- on 80 it is about 35 electrical degrees long. About 1/3 a full > size 1/4 wl vertical . On receive it probably does OK. Heck 3 foot long > active antenna out performs long wires on receive. Transmit is a different > story. Maybe a 40 and 80 dipole will get you better results and again > depends on how high above ground it is.. > > I wouldn't stop using it. Just improve the performance by getting it higher > in the air and choking the coax appropriately, to eliminate RF in the shack. > And run 250 watts into it if you can. It'll take it and that will improve > your radiation strength. > > GL and 73...Rick -- W5R > > Virus-free. www.avast.com > > On Fri, Mar 27, 2020 at 3:42 PM Neal Naumann via BVARC <[email protected]> > wrote: >> Hmmm... MFJ doesn't shed much light on what is in the "matching section". >> Hopefully, it's not a 50 ohm resistor! Maybe it is a 9:1 balun and this is >> like an end-fed wire. But then there is this from the manual "Raise the >> antenna and mast assembly up and mount in the final position. For best >> operation it is recommended that the antenna be put up about 35 >> feet in the air although reasonable results are obtained with a lower >> height". So they are hoping to use the mast as part of the radiator...The >> other problem is that you would like to operate on 80 meters and only have >> 28 feet of antenna. So, I'm not sure where I'm going here with your >> problem. Maybe something in breaking down and arcing in that "matching >> section". If it's a 9:1 balun...that might be why it's only rated at 150 >> Watts CW? >> >> Neal N5EN >> >> On Fri, Mar 27, 2020 at 11:21 AM Martin Blaise <[email protected]> >> wrote: >>> I have a mfj 2386 vertical at my house . It receives okay but transmit is >>> questionable at best. I contacted mfj and asked how to add radials and they >>> said that antenna is designed for without verticals and did I have the >>> bottom of the antenna at 37 feet up? I only have it about less than half of >>> that. I need a taller support. Anyway it’s broadbanded and my 450d internal >>> antenna tuner shows good swr match but last night on 80 meters I tuned up >>> and the antenna matched fine but when I transmitted on cw with flidigi it >>> showed swr mismatch. Rf in the shack? Trouble shooting ideas? Thanks >>> ______________________________________________________________ >>> NARS mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/nars >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >> ________________________________________________ >> Brazos Valley Amateur Radio Club >> >> BVARC mailing list >> [email protected] >> http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org > > > -- > Rick Hiller > e-mail: [email protected] > Cell: 832-474-3713 > Physical: 9031 Troulon Drive > Houston, TX 77036 > > Virus-free. www.avast.com > ________________________________________________ > Brazos Valley Amateur Radio Club > > BVARC mailing list > [email protected] > http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org
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